Sensitivity of processless recording media

ABSTRACT

The process for improving radiant energy sensitivity of a film base coated with a dispersion of a normally crystalline polyacetylenic compound in a non-solvating liquid which is dried on the film surface; said polyacetylenic compound preferably having at least two conjugated acetylenic linkages and containing from 20 to 60 carbon atoms. The process comprises dispersing said normally crystalline polyacetylenic compound in the non-solvating liquid to a concentration of from about 2 to about 50% polyacetylene crystalline solids and ageing said dispersion by (a) storing at a temperature of between about 0° C. and about 12° C. for a period of from about 1 to about 30 days or (b) freezing said dispersion at a temperature between about -78° C. and about -1° C. for a period of from about 1 to about 75 hours or (c) a combination of the above ageing techniques any or all of which are completed before drying said dispersion on a substrate.

This application is a continuation-in-part of co-pending patentapplication Ser. No. 773,487, filed Sept. 9, 1985, now abandoned, in thenames of David F. Lewis, Mark L. Moskowitz and Steward E. Purdy.

DISCUSSION OF THE PRIOR ART

Photosensitive polyacetylenic systems and methods of exposure have beendisclosed in several patents, namely U.S. Pat. Nos. 4,066,676;4,581,315; 3,501,302; 3,501,297; 3,501,303; 3,501,308; 3,772,028;3,844,791 and 3,954,816. Of these polyacetylenic compounds, includingthose of highest sensitivity, the recording of image information haspresented several problems and shortcomings, such as an inadequatedegree of resolution and clarity and color instability of the imagedpattern. Other deficiencies include relatively slow development of theimage and, in certain cases, the need for imaging at extremely lowtemperatures in order to maintain image-receptivity of thepolyacetylenic compound.

Accordingly, it is an object of the present invention to overcome theabove difficulties and deficiencies by a convenient and commerciallyfeasible process.

Another object of the present invention is to provide certainpolyacetylene films which have extremely high sensitivity to radiantenergy exposure.

Another object of the present invention is to provide energy sensitivepolyacetylenic compounds which experience no reversability of colorafter imaging.

These and other objects of the invention will become apparent from thefollowing description and disclosure.

THE INVENTION

According to this invention there is provided a process for improvingthe radiant energy sensitivity of a normally crystalline photosensitivepolyacetylenic compound by introducing said crystals into anon-solvating liquid or binder to form a liquid dispersion containingfrom about 2 to about 50% solids and then ageing said dispersion at atemperature between about -78° C. and about 12° C. for a period of fromabout 0.25 hour to about 30 days. The dispersion may be aged before orafter coating on a film base or substrate; however, such ageing processshould be completed before drying the dispersion on the substrate andimaging.

In the present process it is essential that ageing be effected withpolyacetylene microcrystals dispersed in a liquid medium. The ageing canbe performed on the dispersion per se or on the dispersion after it hasbeen applied to a film base. The liquid medium of the dispersion iswater and any of the subsequently named liquid binders or any othernormally liquid compound or composition in which the crystals areinsoluble as well as any combination of these. The dispersions presentedfor ageing essentially contain from about 1% to about 50%, preferablyfrom about 4% to about 20% by weight of solid polyacetylene. Ageing iseffected in the presence, or for light sensitive compounds, in theabsence of visible light preferably at atmospheric pressure by storingthe dispersion, freezing the dispersion or a combination of freezing andstoring under certain critical time and temperature conditions. Morespecifically, storing the dispersion is effected by allowing thedispersion to stand at a temperature between about 0° C. and about 12°C. for a period of from about 1 to about 30 days, preferably betweenabout 2° C. and about 8° C. for a period of from about 7 to about 15days.

Alternatively the dispersion can be aged in a shorter period by freezingat a temperature between about -78° C. and about -1° C. for a period offrom about 0.25 to about 75 hours, preferably between about -25° C. andabout -10° C. for a period of from about 1 to about 30 hours. It is tobe understood that the duration of freeze ageing is dependent on thetemperature, so that a relatively small sample at -78° C. can be agedeffectively at the lower limit of ageing time, i.e. 0.25 hour. Thefreeze ageing operation involves a phase change in the dispersion sothat the effects are more quickly realized.

A combination of the above methods may also be employed to shortenstorage ageing time. For example, freezing can be effected for up toabout 20 hours and the frozen dispersion gradually allowed to warm up toabout 12° C. where it is held for a period of from about 0.5 to about 10hours.

After the ageing process is completed, the dispersion is allowed to warmto ambient temperature and is dried, or applied and dried, on thesurface of the base film, to form an imaging layer on said base filmsubstrate.

Because the crystal size of commercially available, normally crystallinepolyacetylenes is often relatively large and of varying dimension andsince for the coatings of the present invention a microcrystalline size,between about 0.01 and about 5 micrometers, preferably between about0.05 and about 0.2 micrometers, is most desirable, it is generallyrecommended that the commercial polyacetylene be first dissolved in asolvent from which it can be subsequently recrystallized as finediscrete crystals of a more uniform size. Suitable solvents which can beemployed are those immiscible or slightly soluble in water such as forexample n-butanol, glycol ethers, cyclohexanone and higher molecularweight liquid hydrocarbons. Those which have a relatively low boilingpoint are particularly useful since they can easily be removed byevaporation.

After the crystals are dissolved, the resulting solution is combinedwith an aqueous solution of a binder at an elevated temperature of fromabout 35° C. to about 100° C. with vigorous mixing. The solution canthen be gelled by chill setting at 20°-35° C. within 3 minutes. Thesolvent is then removed, e.g. by evaporation or repeated water washing,whereupon the desired fine crystals are formed and are uniformlydispersed in the binder. Water is added where necessary to assure properdilution of 2-50% solids in the dispersion. To promote betteremulsification of the organic phase in the aqueous phase and therebymore uniform crystals, a minor amount of a conventional surfactant maybe included in the binder solution.

For the purposes of the present invention, it is preferred to employ amulti-layered base film as the imaging medium. When such an imagingmedium is employed in a charged particle beam system, it essentiallycontains a separate conductive layer underlying the polyacetyleneimaging layer consisting of polyacetylene crystals in a binder, and mayalso contain separate support and adhesive layers. However, in certainapplications, where the polyacetylene binder has sufficient integrity atexposure temperatures, the imaging film may consist solely of crystalssuspended in the binder which forms a single layer base film as theimaging medium. Such imaging films can be employed when the imagingenergy source is other than a charged particle beam; in which cases, theneed for a conductive layer is eliminated.

A typical film for the purpose of the present invention comprisesmicrocrystalline polyacetylene in a non-solvating binder forming a layerof from about 0.25 to about 500 micrometers, preferably from about 2 toabout 10 micrometers, thickness which overlays a substrate of from about2 to about 10 mils thickness.

Imaging media suitable for the purposes of the present invention are anyof those commercially available and generally include an electricallyconductive layer of between about 1Å to about 0.25 micrometersthickness, preferably 100Å to about 0.05 micrometers thickness. Althoughtransparent conductive layers of up to about 0.05 micrometers are mostpreferred, opaque conductive layers of up to 5 micrometers can also beemployed when need arises. The conductive layer limits the capacitanceof the charge accepting layer, namely the image-receptive polyacetyleniccrystals dispersed in binder, and typically has a resistivity of 10⁶ohms/square or less. The conductive material is an electricallyconductive metal, metal oxide, metal alloy, metal halide or carbon blackwhich metal, metal compound and carbon black components may or may notbe suspended in a dispersion medium such as gelatin, dextran, acellulose ether or ester or any other conventional suspension medium.Suitable metals include gold, silver, platinum, copper, iron, tin,aluminum, indium, nickel, palladium, rhodium and mixtures of these asmay occur in alloys and metal oxides or halides. A specific metal oxidewhich may be suitably employed includes indium-tin oxide. Silver bromideand copper iodide are representative of the metal halides which may beused as the conductive layer. Of these conductive materials, indium-tinoxide is most preferred.

The conductive layer is usually supported by a substrate of betweenabout 0.25 and about 100 mils, preferably 0.5 to 10 mils, thickness.Suitable materials employed as substrates include polyester,polyethylene terephthalate, glass, clay-sized paper, fiberboard, metalsheeting, glazed ceramic, cellulose acetate, polystyrene, polycarbonatesor any other conventional support.

The substrate or support can be flexible or rigid, opaque or transparentdepending on the final use of the film. Particularly preferred are thecommercial polyester substrates such as MYLAR (polyethyleneterephthalate), supplied by E. I. du Pont Corporation and HOSTAPANsupplied by American Hoechst.

The image-receptive layer generally overlays a supported conductivelayer, and in certain cases is more firmly affixed thereto by means of athin adhesive layer having a thickness of between 1 and 1.5 micrometer.When used, suitable adhesives include acrylate based polymers andcopolymers, particularly those containing carboxylate moieties such asacrylic acid or methacrylic acid residues and mixtures of these polymersor copolymers with gelatin.

In certain cases, when a conductive metal sheet is employed as thesubstrate, a separate conductive layer may be eliminated and theimage-receptive layer disposed directly on the metal sheet conductivesupport.

The image receptive layer, which is the surface layer of the imagingfilm, comprises the polyacetylenic microcrystals dispersed in a bindermaterial. The polyacetylenic compounds of the present invention arenormally crystalline at ambient temperature and are preferablyconjugated diynes, most preferably hydrocarbon or acid diynes containingfrom 20 to 30 carbon atoms. A general formula for these preferredacetylenic compounds is, represented by the structure A--(CH₂)_(n)--C.tbd.C--C.tbd.C--(CH₂)_(m) --B wherein m and n are both independentlyan integer of from 6 to 14 and A and B are independently methyl orcarboxyl groups. Specific examples of such polyacetylenes includepentacosa-10,12-diynoic acid; 13,15-octacosadiyne anddocosa-10,12-diyne-1, 22-dioic acid. Of these, the agedpentacosa-10,12-diynoic acid is most preferred since it providesunusually high sensitivity to electron beam exposure. It is to beunderstood however, that dispersions of other normally crystalline,color developing polyacetylenes having a conjugated structure can beemployed alone or in admixture with the preferred diynes as the imagereceptive layer of the present invention. Such compounds include thediynes of the above structure wherein the A and/or B moieties, inaddition to lower alkyl or carboxyl, also can be hydroxy, amido, loweralkyl substituted amido, an aliphatic or aromatic carboxylate estergroup having up to 10 carbon atoms, a mono- or di- valent carboxylatemetal salt group, halo, carbamyl, lower alkyl substituted carbamyl ortosyl, as well as the corresponding triyne and tetrayne products of theabove polyacetylenes having from 20 to 60 carbon atoms and a conjugatedstructure. Examples of these compounds include 10,12-docosadiynediol,the ditoluene-p-sulfonate of 9,11-eicosadiynoic acid, the monoethylester of 10,12-docosadiynedioic acid, the sodium or potassium salt of10,12-pentacosadiynoic acid, 10,12-docosadiyne chloride,10,12-pentacosadiyne (m-tolyl- urethane), 10,12-pentacosadiyne{[(butoxylcarbonyl)- methyl]urethane},N-(dimethyl)-10,12-pentacosadiynamide, N,N'-bis(α-methylbenzyl)10,12-pentacosadiyndiamide, etc. The polyacetylenic compounds of thisinvention are employed in microcrystalline form and these crystals aredispersed, in a non-solvating liquid binder preferably an aqueoussolution of plastic, resin, colloid or gel and coated on a suitableconductive substrates to a layer thickness of from about 0.25 to about500 micrometers. On drying, the crystals become fixedly positioned inthe binder.

Exemplary binder materials include natural and synthetic plastics,resins, waxes, colloids, gels and the like including gelatins, desirablyphotographic-grade gelatin, various polysaccharides including dextran,dextrin, hydrophilic cellulose ethers and esters, acetylated starches,natural and synthetic waxes including paraffin, beeswax,polyvinyl-lactams, polymers of acrylic and methacrylic esters andamides, hydrolyzed interpolymers of vinyl acetate and unsaturatedaddition polymerizable compounds such as maleic anhydride, acrylic andmethylacrylic esters and styrene, vinyl acetate polymers and copolymersand their derivatives including completely and partially hydrolyzedproducts thereof, polyvinyl acetate, polyvinyl alcohol, polyethyleneoxide polymers, polyvinylpyrrolidone, polyvinyl acetals includingpolyvinyl acetaldehyde acetal, polyvinyl butyraldehyde acetal, polyvinylsodium-o-sulfobenzaldehyde acetal, polyvinyl formaldehyde acetal, andnumerous other known photographic binder materials including asubstantial number of aforelisted useful plastic and resinous substratematerials which are capable of being placed in the form of a dope,solution, dispersion, gel, or the like for incorporation therein of thephotosensitive polyacetylenic composition and then capable of processingto a solid form containing dispersed crystals of the photosensitivecrystalline polyacetylenic composition of matter. As is well known inthe art in the preparation of smooth uniform continuous coatings ofbinder materials, there may be employed therewith small amounts ofconventional coating aids as viscosity controlling agents, surfaceactive agents, leveling agents, dispersing agents, and the like. Theparticular binder material employed is selected with due regard to thespecific radiant energy and technique to be employed in the particularimage-recording application and invariably is a binder materialpermitting substantial transmission or penetration of that specificradiant energy to be employed.

The radiant energy contemplated as the energy source in the presentinvention includes energy generated from an electron beam such asdeveloped by cathode ray guns, gamma rays and X-rays used inradiography, beta rays, electron corona discharge, ultra-violet andlight, actinic radiation from visible and infra-red regions of theelectromagnetic spectrum and other forms of corpuscular and/or wave-likeenergy generally deemed to be radiant energy. For radiographic and shortwave UV exposure, the conductive layer in the above dielectric film maybe eliminated and the image-receptive crystals in the binder may bedisposed directly on the substrate material; although absence of theconductive layer may permit the film to become so charged that a beam ofelectrons or ions employed for imaging may be somewhat distorted.

The preferred source of energy employed in the present invention is theelectron beam. Generally the electrons, under high vacuum, between about10⁻³ and about 10⁻⁹ torr, preferably between about 10⁻⁵ and about 10⁻⁸torr, bombard the surface of the film, thus transmitting an imagethereon for development into an optical display. The techniques ofelectron beam recording are well known, thus further amplification isnot required. However, for illustrative purposes, a typical electronbeam recording operation suitable for the present invention may utilizean electron beam characterized by having a beam diameter of from about 1to 25 micrometers, an energy of from about 10 to 30 KeV, a current flowof from about 10⁻⁹ to 10⁻⁶ amps and adapted to scan a target area at arate such that the dwell time is from about 10⁻³ to 10⁻⁸ seconds. Vacuumpressures in the film chamber commonly range from 10⁻³ to 10⁻⁵ torr.

In one embodiment of the invention, an aged dispersion of thepolyacetylene crystals in binder is applied to the surface of a basefilm and dried thereon at a temperature of from about ambienttemperature up to about 100° C. but below the distortion temperature ofthe substrate or binder, and below the decomposition temperature ormelting point of the polyacetylene compound. The drying operation isconducted over a period of from about 20 seconds to about 10 hours andis preferably effected at 15° to 60° C. for a period from about 1 minuteto about 5 hours.

Upon exposure of the coated base film to the image transmitted from aradiant energy source, the aged and dried polyacetylene crystals,fixedly positioned in the binder, undergo a color change in the exposedareas to provide a replica of the transmitted image or pattern of theexposure in high resolution and contrast to the unexposed background.The color change occurs almost instantaneously or within a period of upto 2 days and the image is transmitted directly to the film without needfor extraeneous development. By employing the ageing process of thepresent invention, an image receiving layer of up to 6×10⁻⁸ C/cm² andhigher sensitivity, defined as the dosage of 20 KeV electrons requiredto produce a visual density of 2, can be obtained. Also, a maximumdensity greater than 4 can be achieved.

Having thus described the invention, reference is now had to thefollowing examples which illustrate preferred embodiments of theinvention but which are not to be construed as limiting to its scopewhich is more broadly defined above and in the appended claims.

EXAMPLE 1 PREPARATION OF DISPERSION

In a glass beaker, 15 g of pentacosa-10,12-diynoic acid non-uniformcrystals were dissolved at 38° C. in 45 g of ethyl acetate to form asolution, Solution A. A second solution, Solution B, was prepared bydissolving 15 g of photographic gelatin in 250 g of water and 30 ml ofan aqueous solution containing 3% by weight of surfactantGAFAC-RS-710.sup.(1). Solution B was heated to 40° C. and introducedinto a 1 quart size Waring blender. While blending at high speed,Solution A was added to Solution B over about a 30 second period.Blending was continued for an additional 2.5 minutes before pouring ontoa stainless steel tray where it was allowed to chill set. The resultinggelled dispersion was cut into approximately 1 cm cubes and allowed tosit in an airstream at about 32° C. to remove ethyl acetate byevaporation. After the ethyl acetate had been removed, the gelleddispersion was reconstituted by melting at 40° C. and adding sufficientwater to replace the weight loss that occurred during drying. Theaverage crystal size was between about 0.05 and about 0.22 micrometers.

EXAMPLE 2 COATING THE FILM BASE

The reconstituted dispersion prepared in Example 1 was melted anddirectly coated at about 10 micrometers thickness on a 4 mil film base,SIERRACIN INTREX-K .sup.(2). which is a polyester base carrying anindium-tin oxide conductive coating which had been overcoated with a 1micrometer thick layer of an adhesion promoting material composed ofabout 50 wt. % gelatin and 50 wt % of a latex polymer. The coated filmwas then allowed to dry in air at ambient temperature. After drying wascompleted, the coated film was exposed to 20 KeV electron imaging untila blue image of the transmitted information formed. The image on thedried dispersion layer had a maximum density of 3.35 and a sensitivityof 2.7×10⁻⁷ coulombs/cm² (3).

EXAMPLE 3

Five samples of coated film base, prepared as in Examples 1 and 2, wereprepared and labeled, e.g. 3A-3E. Each of these samples was exposed to20 KeV electron beam imaging and the maximum density and sensitivity ofthe resulting imaged film was determined as shown in the following TableI.

                  TABLE I                                                         ______________________________________                                        Sample   Maximum Density                                                                             Sensitivity × 10.sup.-7 C/cm.sup.2               ______________________________________                                        Example 1                                                                              3.35          2.7                                                    3A       2.80          7.5                                                    3B       2.96          5.7                                                    3C       3.40          2.8                                                    3D       2.93          5.7                                                    3E       2.74          8.0                                                    ______________________________________                                    

Although all of the above samples were made in the same way, withidentical materials, the data shows a high variation of results whichestablish the unpredictability of density and sensitivity when employingthe procedure of Examples 1 and 2.

EXAMPLE 4

Three dispersion samples, (4A, 4B and 4C) were prepared as in Example 1.Each of the samples was divided into 2 portions. The first portion ofeach sample was coated directly on the film base as in Example 2, whilethe second portions were each refrigerated at about 4° C. for a periodof 18 days and then coated on the film base as in Example 2. All sampleswere exposed to 20 KeV electron beam imaging and the sensitivities(×10⁻⁷ C/cm²) of the imaged films were then determined, the results ofwhich are shown in Table II.

                  TABLE II                                                        ______________________________________                                                 SENSITIVITY, × 10.sup.-7 C/cm.sup.2                            Sample     Non-Aged Coating                                                                            Aged Coating                                         ______________________________________                                        4A          1.6          1.4                                                  4B         13.0          1.2                                                  4C         13.0          1.3                                                  ______________________________________                                    

Again, the above data show the inconsistent sensitivity of filmsdirectly coated with the freshly prepared imaging dispersion. The dataalso demonstrate that ageing results in increased sensitivity at highlyreproducable values.

EXAMPLE 5

Samples 5A, 5B and 5C were prepared according to the procedure ofExample 1. Seven equal portions of each sample were taken. The first wasdirectly coated on the film base as described in Example 2. Theremaining portions were aged at about 4° C. for various periods up to 25days, as shown in Table III before coating the film base as in Example2. Each of the sample portions was exposed to 20 KeV electron beamimaging after which sensitivity was determined as shown in the followingTable.

                  TABLE III                                                       ______________________________________                                        Ageing Period                                                                           SENSITIVITY, C/cm.sup.2                                             (days)    5A           5B        5C                                           ______________________________________                                        none      1.2 × 10.sup.-6                                                                      5.4 × 10.sup.-7                                                                   9.1 × 10.sup.-7                         1        1.0 × 10.sup.-6                                                                      4.0 × 10.sup.-7                                                                   1.0 × 10.sup.-6                         4        --           --        1.0 × 10.sup.-6                         8        1.9 × 10.sup.-7                                                                      3.8 × 10.sup.-7                                                                   8.0 × 10.sup.-7                        12        1.9 × 10.sup.-7                                                                      2.5 × 10.sup.-7                                                                   4.5 × 10.sup.-7                        15        1.8 × 10.sup.-7                                                                      1.0 × 10.sup.-7                                                                   3.0 × 10.sup.-7                        25        1.8 × 10.sup.-7                                                                      2.0 × 10.sup.-7                                                                   2.8 × 10.sup.-7                        ______________________________________                                    

This data illustrates the progressive increase in sensitivity on ageingand also show that the benefit obtained from ageing reaches a threshold(at about 15 days) beyond which there is no significant increase insensitivity. It is also noted that there is no degradation of thedispersion due to storage for longer periods.

EXAMPLE 6

Two samples were prepared according to Example 1 and each was directlycoated on a film base according to Example 2. Each of these samples wereimaged by a UV light source at short wave UV radiation of 254 nanometersusing the increasing exposure times noted in Table IV. Blue images wereformed and the densities of these images were recorded. The samples werethen aged for 2 weeks at about 4° C. and the same exposures from thesame UV light source were repeated. Again the densities of the imageswere recorded. The results of this experiment are shown in Table IV.

                  TABLE IV                                                        ______________________________________                                        VISUAL DENSITY                                                                Exposure time                                                                 (minutes)  Non-Aged Coating                                                                            2-Week Aged Coating                                  ______________________________________                                        1          0.24          0.28                                                 2          0.71          0.70                                                 3          0.72          0.75                                                 4          0.83          0.85                                                 5          0.89          0.92                                                 ______________________________________                                    

The above data show that the process provides no benefit when ageing thepolyacetylene in binder after drying. Accordingly, ageing the dispersioncontaining 2 to 50% polyacetylene crystals, in a wet state, is acritical consideration in the present process.

EXAMPLE 7

Example 6 was repeated except that one sample was aged at about 4° C.for 2 weeks before drying on the film base while the remaining samplewas directly coated on the film without ageing. The results of thesesamples, when exposed to the same UV light source, are compared with thenon-aged samples of Example 6 as shown in the following Table V.

                  TABLE V                                                         ______________________________________                                        VISUAL DENSITY                                                                Exposure Time             Aged Coating in                                     (minutes)   Non-aged Coating                                                                            wet state                                           ______________________________________                                        1           0.24          0.81                                                2           0.71          1.36                                                3           0.72          1.79                                                4           0.83          2.02                                                5           0.89          2.15                                                ______________________________________                                    

The above results show a remarkable improvement in density when ageingthe dispersion in the wet state.

EXAMPLE 8

Three samples (8A, 8B and 8C) were prepared according to Example 1. Thedispersion of Sample 8A was directly coated on the base film withoutageing and dried thereon as described in Example 2. The dispersion ofSample 8B was frozen at about -15° C. for a period of 2 hours; whereasthe dispersion of Sample 8C was frozen at about -15° C. for a period of3 days.

After freezing, the dispersions of 8B and 8C were allowed to warm toroom temperature after which they were coated on separate base films anddried thereon as described in Example 2.

All three samples were exposed by imaging with UV light (short wave UVradiation of 254 nanometers). The following image densities wereobtained.

                  TABLE VI                                                        ______________________________________                                        Exposure Time                                                                              VISUAL DENSITY                                                   (minutes)    8A          8B     8C                                            ______________________________________                                        1            0.12        0.82   0.86                                          2            0.22        1.53   1.51                                          3            0.37        1.92   1.89                                          4            0.46        2.15   2.09                                          5            0.40        2.22   2.18                                          ______________________________________                                    

The above results establish the remarkable improvement of image densityachieved by freezing the dispersion prior to drying on the base film.The data also shows that substantially the same degree of densityimprovement is realized after 2 hours up to 3 days or longer but thatthe dispersion is in no way degraded by the longer freezing period.Comparing the results for 8B with those for the aged sample set forth inExample 7, it becomes evident that the effective ageing of thedispersion is significantly accelerated when freezing is employed as theageing process.

EXAMPLE 9

The preceding Example 8A was repeated except that Sample 8A was frozenat -15° C. for 12 hours after being dried on the base film. This samplewas designated as Sample 9 and comparison of visual density found forSample 9 and sample 8A of the preceding example are presented in TableVII.

                  TABLE VII                                                       ______________________________________                                        Exposure Time   VISUAL DENSITY                                                (minutes)       8A       Sample 9                                             ______________________________________                                        1               0.12     0.17                                                 2               0.22     0.32                                                 3               0.37     0.47                                                 4               0.46     0.58                                                 5               0.40     0.62                                                 ______________________________________                                    

As in the case of electron beam imaging, the data in this example showsno significant improvement of the non-aged sample when the freezing iseffected on a dryed coating.

EXAMPLE 10

The preparation of Example 1 is repeated except that drying to removeethyl acetate and reconstitution with water were omitted.

The dispersion was coated to 10 micrometers thickness on base filmSIERRACIN INTREX-K as in Example 2 and was then chill set and frozenovernight at -15° C. The coated film was then thawed and dried at about50° C.

This sample was exposed to UV light (short wave UV radiation of 254nanometers) and visual density observed and recorded as in the followingTable VIII. The density of this product is compared so that of Example8A as shown.

                  TABLE VIII                                                      ______________________________________                                        Exposure Time  VISUAL DENSITY                                                 (minutes)      Sample 8A Sample of Ex. 9                                      ______________________________________                                        1              0.12      0.19                                                 2              0.22      0.40                                                 3              0.37      0.57                                                 4              0.46      0.70                                                 5              0.40      0.78                                                 ______________________________________                                    

The data shows that the presence of the solvating liquid in thedispersion during ageing prevents development of full sensitivity. Thus,it is important to remove the solvent before ageing and permitcrystallization of the polyacetylene in uniform microcrystals.

EXAMPLE 11

Two dispersions are prepared using the method of Example 1 except that13,15-octacosadiyne and docosa-10,12-diyne-1,22-dioic acid aresubstituted for pentacosa-10,12-diynoic acid.

Each of the samples of this example is divided into two equal portions;one portion being coated immediately on film according to the method ofExample 2 and the remaining portion of each sample being aged byfreezing at -15° C. overnight. The frozen portions are warmed to ambienttemperature, melted and then coated on film as in Example 2. Each of theabove portions are then exposed to a 20 KeV electron beam source torender an image on the surface. A substantial increase in sensitivity ofthe coatings prepared from the aged frozen dispersions is observed incomparison to the sensitivity resulting from the non-aged coatings ofthe corresponding diacetylene compounds.

What is claimed is:
 1. A process for improving radiant energysensitivity of an image-receptive, normally crystalline polyacetylenecompound which comprises: (a) dispersing the polyacetylene microcrystalsin a non-solvating liquid to form a liquid dispersion containing fromabout 1 to about 50% polyacetylene solids and (b) ageing said dispersionat a temperature between about -78° C. and about 12° C. for a period offrom about 0.25 hour to about 30 days and completing said ageing beforedrying said dispersion prior to imaging with said radiant energy.
 2. Theprocess of claim 1 wherein the aged dispersion is coated on the surfaceof a substrate, the coating is dried and subjected to radiant energyexposure for imaging.
 3. The process of claim 2 wherein the substrate isan electrically conductive polyester film.
 4. The process of claim 1wherein the non-solvating liquid is water and a non-solvating binder inwhich the polyacetylene microcrystals are dispersable.
 5. The process ofclaim 4 wherein the liquid medium of the dispersion is a mixture ofwater and binder and wherein the binder is gelatin.
 6. The process ofclaim 1 wherein the polyacetylene is a conjugated diyne compound havingfrom 20 to 30 carbon atoms.
 7. The process of claim 6 wherein said diynecompound contains from 0 to 2 carboxyl groups.
 8. The process of claim 6wherein the diyne has the formula:

    CH.sub.3 (CH.sub.2).sub.11 --C.tbd.C--C.tbd.C--(CH.sub.2).sub.8 --COOH.


9. The process of claim 6 wherein said diyne has the formula:

    CH.sub.3 (CH.sub.2).sub.11 --C.tbd.C--C.tbd.C--(CH.sub.2).sub.11 CH.sub.3.


10. The process of claim 6 wherein said diyne has the formula:

    HOOC--(CH.sub.2).sub.8 --C.tbd.C--C.tbd.C--(CH.sub.2).sub.8 --COOH.


11. The process of claim 4 wherein the ageing comprises storing saidcrystals dispersed in said liquid medium at a temperature between about0° C. and about 12° C. for a period of from about 1 to about 30 daysbefore drying.
 12. The process of claim 4 wherein said ageing comprisesfreezing said crystals dispersed in the liquid medium at a temperaturebetween about -78° C. and about -1° C. for a period of from about 0.25to about 75 hours before drying.
 13. The process of claim 4 wherein themicrocrystals dispersed in the liquid medium are frozen at a temperaturebetween about -78° C. and about -1° C. for a period up to about 20 hoursand then stored at a temperature between about 0° C. and about 12° C.for a period of from about 0.5 to about 10 hours before drying.
 14. Theprocess wherein the polyacetylene microcrystals are dispersed in aliquid binder and the dispersion forms the surface layer of an imagingfilm and said film is subjected to the ageing process of claim
 11. 15.The process wherein the polyacetylene microcrystals are dispersed in aliquid binder and the dispersion forms the surface layer of an imagingfilm and said film is subjected to the ageing process of claim
 12. 16.The process wherein the polyacetylene microcrystals are dispersed in aliquid binder and the dispersion forms the surface layer of an imagingfilm and said film is subjected to the ageing process of claim
 13. 17.The process of claim 6 wherein a conjugated diyne compound of 22 to 28carbon atoms and having a terminal carboxyl group is dispersed in anon-solvating liquid binder to provide a liquid medium containing fromabout 4% to about 20% polyacetylene microcrystalline solids and thedispersion is aged by storing at a temperature between about 2° C. andabout 8° C. for a period of from about 7 to about 15 days.
 18. Theprocess of claim 6 wherein a conjugated diyne compound of 22 to 28carbon atoms and having a terminal carboxyl group is dispersed in anon-solvating liquid binder to provide a liquid medium containing fromabout 4% to about 20% polyacetylene crystalline solids and thedispersion is aged by freezing at a temperature between about -25° C.and about -10° C. for a period of from about 1 to about 30 hours. 19.The process of claim 18 wherein the dispersion, after freezing, isallowed to warm to ambient temperature and is then melted, coated anddried on a film base prior to imaging.
 20. The process of claim 17wherein the dispersion, after storing, is directly coated and dried on afilm base prior to imaging.
 21. The process of claim 17 wherein saiddiyne is selected from the group consisting of pentacosa-10,12-diynoicacid, docosa-10,12-diyne-1,22-dioic acid and 12,15-octacosadiyne. 22.The process of claim 18 wherein said diyne is selected from the groupconsisting of pentacosa-10,12-diynoic acid,docosa-10,12-diyne-1,22-dioic acid and 12,15-octacosadiyne.
 23. Theproduct of the process of claim
 1. 24. The composition comprisingbetween about 4% and about 20% microcrystalline pentacosa-10,12-diynoicacid dispersed in aqueous gelatin and aged at a temperature betweenabout -25° C. and about 12° C. for a period of from about 5 hours toabout 15 days.
 25. A recording film suitable for imaging by exposure toa source of radiant energy which comprises a film base on which iscoated and dried the aged dispersion of claim
 24. 26. The compositioncomprising between about 2 and about 50% of a normally crystallineconjugated polyacetylene compound dispersed in microcrystalline form ina non-solvating liquid and aged at a temperature of between about -78°C. and about 12° C. for a period of from about 0.25 hour to about 30days.
 27. A recording film suitable for imaging by exposure to a sourceof radiant energy which comprises a film base on which is coated anddried the aged dispersion of claim
 26. 28. The process of claim 1wherein the polyacetylene microcrystals suitable for said dispersion areproduced by dissolving polyacetylene crystals of a larger non-uniformsize in a solvent, subjecting the resulting solution to chill setremoving said solvent, recrystalizing polyacetylene crystals of moreuniform microcrystaline size of between about 0.01 and about 5micrometers.
 29. The process of claim 1 wherein said ageing is effectedfor a period of from about 1 hour to about 30 days.